Mice are a huge issue in almost every DC school. I am not sure why DCPS cannot get the mice under control.
You probably should write to whoever in DCPS central is in charge of custodial services.
Or ask about it as a general issue on the Chancellor's twitter forum. It goes beyond the principal as every HS is overrun by mice.

In general, our principal replies same-day for important/quick items, and within a week for slower track stuff. In the last few weeks of the year I would cut them some slack, and who could begrudge them a day or two off after the final week? But in general, same day or within less than 5 days.

Email this address: dcps.earlychildhood@dc.gov and explain your concern. The Head Start Quality Assurance team is based in Central Office, and they're usually involved when there are health and safety issues in the classroom. They can check their database to see whether the mice droppings have been reported by the teachers, and then reach out to the principal from their end.